URL parameters: Why difficult / impossible with CI?

[eluser]Unknown[/eluser]
I'm writing an application that must take in a few parameters from the URL. That means I must accept them as traditional name/value pairs. Example:

myfile.php?name=jon&color=blue

The end user may want to pass me a few more name/value pairs too.. but the other ones are optional.. for example:

myfile.php?name=jon&color=blue&age=55&state=CA

It seems like code igniter requires me to use slash notation. What's the correct way for me to pass this stuff with CI's slash notation so that the variables are accessable by their names. For example:

$_GET["state"]

Thank you!
Jon